Heat regenerator



Nov. 6, 1962 J. MULDER HEAT REGENERATOR 2 Sheets-Sheet 1 Filed May 29,1953 R mu NI- U V M mN AGENT 3,%Z,509 Patented Nov. 6, 1962 free3,062,509 HEAT REGENERATOR Jan Mulder, Eindhoven, Netherlands, assignor,by mesne assignments, to North American Philips Company, Inc, New York,N.Y., a corporation of Delaware Filed May 29, 1953, Ser. No. 358,510

Claims priority, appiication Netherlands Feb. 12, 1953 1 Claim. (Cl.257270) The invention relates to a regenerator comprising wire material,having a hydraulic diameter of less than 200 The term hydraulic diameteris to be understood to mean herein the quotient of four times thesurface area divided by the circumference of the cross-section of thewire material. Wire-regenerators are known per se; it is known, forexample, to manufacture regenerators by coiling metal wire formed or notformed by crinkles.

It is furthermore known that the output of a regenerator may be enhancedby reducing the diameter of the wire. This measure is applied to theknown regenerators, so that they are frequently manufactured from Wirematerial having a hydraulic diameter of less than 50g.

The applicant has now found that not only the wire diameter, but alsothe degree of inhomogeneity of the regenerator exerts great influence onthe output thereof.

The inhomogeneity of the regenerators hitherto known is comparativelyhigh; locally differences of 20% and more may occur. The inhomogeneitymay be ascertained by taking a radiograph of a layer of regeneratormaterial of uniform thickness.

The applicant has now found by surprise that the homogeneity of aregenerator invented by the applicant materially exceeds that of theknown regenerators. The local filling factor of the regeneratoraccording to the invention may deviate not more than 5% from the meanvalue of the filling factor. The term filling factor is to be understoodto mean herein the ratio between the volume of the wire material and thevolume of the regenerator.

The regeneratoraccording to the invention, comprising wire materialhaving a hydraulic diameter of less than 200a, has the feature that itcomprises a large number of metal wire portions, having a substantiallyuniform wire profile, the maximum length of these wire portions beingcm., the minimum length 2 mm., whilst the regenerator exhibits asubstantially homogeneous felt-like structure. Where reference is madeherein to a felt-like structure, this is to be understood to mean astructure resembling felt macroscopically, it being, however, notrequired for the wire portions to be secured to one another as is, ingeneral, the case in felt manufacture. As a wire material for theregenerator according to the invention use may be made of a materialhaving a circular, rectangular or other transverse profile.

Regenerators according to the invention are preferably used in hot-gasreciprocating engines. The term hot-gas reciprocating engine is to beunderstood to mean herein a hot-gas reciprocating apparatus, arefrigerator and a heat pump, the latter two operating on the reversedhotgas reciprocating engine principle.

In one embodiment of the invention the wire portions are secured to oneanother. The portions may, for example, be secured to one another bysintering. As an alternative, the Wire portions may be coated by a metallayer, by means of which the wire portions are secured to one another byheating. By securing the wire portions to one another the structure ofthe filling mass is, however, not modified.

In a further embodiment of the invention the regenerator has the featurethat the cross sectional area of the wire portions has a hydraulicdiameter of not more than 50g, whilst the filling factor of theregenerator varies between 3% and 30%, preferably between 5% and 20%.

The regenerator according to the invention may be formed by layers,which are arranged substantially transversely to the main direction offlow of the gas through the regenerator.

In certain cases it may be advantageous in a further embodiment of theinvention to provide curled portions or crinkle-wire. The term crinklewire is to be understood to mean herein a deformation of the wire suchthat the wire exhibits a periodical change in shape; the wire may, forexample, be zigzagged.

The regenerator according to the invention may be manufactured in asimple manner. The wire portions may, for example, be distributed in aspace in a manner such that a layer of substantially uniform thicknessis formed on the bottom of this space, after which this layer iscompressed in order to obtain the required filling factor.

The wire portions are preferably transported by means of a turbulentflow of air to the space. Owing to the turbulence of this flow of air,the wire portions are distributed chaotically, which materially furthersthe homogeneity of the regenerator.

The device for manufacturing the regenerator according to the inventionhas the feature that it comprises a space having a cross sectional areaof a shape and a size substantially corresponding to those of the crosssectional area of the regenerator to be manufactured, a downcomercommunicating with the space and means for supplying the wire portionsthereto.

In a further embodiment of the invention the device comprises at leastone spray mouth for supplying the wire material and a space having across sectional area, of which the shape and the size correspondsubstantially to those of the cross sectional area of the regenerator tobe manufactured, this space having on one side a wall which is perviousto gas, whilst the spray mouth communicates with the space through adowncomer.

A structurally simple construction may be obtained by providing thedevice with a cutting member, by means of Which wire portions of thedesired length are cut from sheet material or wire material, theseportions being supplied to the space. The spray mouth and the space arepreferably caused to rotate relatively to one another.

In order that the invention may be readily carried into efiect, it willnow be described with reference to the accompanying drawing, which showsa regenerator according to the invention, a hot-gas reciprocating enginecomprising such a regenerator and a device for manufacturing theregenerator.

FIG. 1 is a plan view of a regenerator according to the invention andFIG. 2 is a sectional view of this regenerator taken on the line IIII ofFIG. 1.

FIG. 3 shows a hot-gas reciprocating engine comprising such aregenerator.

FIG. 4 shows a device by means of which the regenerator according to theinvention may be manufactured.

FIGS. 1 and 2 show a regenerator according to the invention. Thisregenerator comprises wire material I, having a diameter of less than200a. It is made from a large number of metal wire portions, having asubstantially uniform wire profile, the maximum length of these Wireportions being 10 cm., the minimum length 2 mm. In the regenerator shownthis length may, for example, be 3 cm., whilst the hydraulic diameter is60 The regenerator exhibits a felt-like structure. The regenerator shownmay be sintered, so that the wire portions adhere to one another; thestructure is, however, not modified, so that this sintering or themetallisation does not affect the porosity of the regenerator. As isshown in the figure, the regenerator may be surrounded by twocylindrical walls 2 and 3 and may comprise a plurality of layers 4. Thewire portions of the regenerator shown are arranged substantiallytransversely to the main direction of How of the gas; this direction isindicated by the double arrow 5.

FIG. 3 shows a hot-gas reciprocating engine comprising a regeneratoraccording to the invention. The hot-gas recip rg cating engine is of thedisplacer-piston type and comprises a displacer piston and a piston 11,reciprocating with constant phase difference. By means of aconnecting-rod system 12 the displacer piston 10 is coupled with a crankof the crank shaft 13. The piston 11 also is coupled by means of aconnecting-rod system 14, with a crank of the same crank shaft. Thespace 15 is the hot space of the hot-gas engine and this spacecornmunicates through a heater 16, a regenerator 17 and a cooler 18 withthe space 19 between the displacer piston 10 and the piston 11. Theregenerator 17 is of the type described above and has a filling factorvarying between 3% and 30%, for example, a filling factor of 13%.

FIG. 4 shows a device by means of which the regenerator according to theinvention may be manufactured. The device comprises a space having anouter wall 20 and a core 21. The cross sectional area of the space 22between the outer wall 20 and the core 21 has a shape and a sizecorresponding substantially to the shape and the size of the crosssectional area of the regenerator to be finally manufactured. This space22 is provided at the bottom with a wall 23 pervious to gas. The wall 20is provided on the outer side with a toothed rim 24, which engages aWorm 25 of an electric motor 26. The wall 20 and the core 21 arerotatable about their vertical axis and secured to a structure 27. Atthe top provision is made of a lid 28, through which is taken a supplypipe 29, relatively to which the wall 20 is adapted to rotate. Thesupply pipe 29 communicates with a duct 30, which communicates in turnwith a device 31, in which the wire material to fill the space 22 is cutinto portions of substantially equal lengths. The device 31 comprises ahousing 32, in which a body 33 is adapted to rotate. This body isprovided with knives 34, which are urged against the wall 36 of thehousing by means of springs 35. The body 33 is provided with a shaft 37,on which is seated a rope disc 38, so that the body 33 can be rotated bymeans of the rope 39 by the motor 40.

The wall 36 has an opening 41 which communicates with a narrow duct 42.The latter communicates with the duct 43, which has a materially largercross sectional area and which is provided in the wall opposite the duct42 with a small aperture 44. Through the aperture 44 may be taken a wire45 extending as far as in the duct 42. The wire 45 is led over theroller 46 and coiled on the supply coil 47. The duct 43 communicatesWith the duct 48 of a compressor 49, which may be driven by a motor 50.

The housing 32 has an opening 51, which communicates through the airduct 48 with the compressor 49.

The device operates as follows. The air supplied through the duct 43,having, for example, a pressure of 4 atmospheres, transports the wire 45through the duct 42, the wire thus passing through the opening 41, thusex- 4 tending beyond the wall 46. The rotating body 32 periodically cutsoff portions from this wire, these portions being transported by the airsupplied through the duct 48 and caused to turbulate, through the duct30 to the space 22. During the transit in the duct 29, the wire portionsare set into turbulence. Since the quantity of air supplied through theduct 48 is comparatively small, it will have little or no influence onthe motion of the wire portions in the materially larger space 22. Thewire portions are distributed from the pipe 29 in the rotating space 20,so that the pervious Wall 23 of this space has a uniform felt-like layerformed on it. The length of the Wire portions is in this case not morethan 10 cm. and not less than 2 mm., whilst the hydraulic diameter ofthe wire is smaller than 2007.0 and may, for example, be 3011. When thespace 22 is filled with a sufiiciently thick layer, the topside of thespace may be removed and the layer may be compressed to the desiredfilling factor lying between 3% and 33%, preferably between 10 and 25%.

In the device described above three motors are provided, driving thecompressor, the cutting member and the space 20 respectively. If desiredthe three said parts may be driven by one motor.

By means of the device shown in FIG. 4 regenerators may be made havingan annular cross sectional area, as is shown in FIGS. 1 and 2. However,as an alternative, regenerators having other cross sectional areas, forexample, a circular sectional area, may be manufactured in the samemanner. In this case the space 22 does not comprise a core 21.

Claims directed to an apparatus for and a method of making myregenerator are being presented in my copending US. patent application,Ser. No. 778,249, filed December 4, 1958.

What is claimed is:

A regenerator for a hot-gas reciprocating engine comprising a housinghaving an inlet opening and an outlet opening for a gaseous workingmedium adapted to flow along a path therebetween, a felt-like mass insaid path and having a substantially homogeneous structure with afilling factor between about 3 and 30%, said mass comprising metal wireportions of substantially unifomn cross section and of lengths betweenabout 2 mm. and mm. depending upon the shape and size of theregenerator, said metal wire portions having a hydraulic diameter lessthan about 200 microns and extending in random directions substantiallyin planes perpendicular to the flow path.

References Cited in the file of this patent UNITED STATES PATENTS1,808,921 Frankl June 9, 1931 2,201,180 Jordan May 21, 1940 2,217,766Meff Oct. 15, 1940 2,401,797 Rasmussen June 11, 1946 2,454,241Wennerberg Nov. 16, 1948 2,564,100 Du Pre Aug. 14, 1951 2,616,668 VanWeenen et al Nov. 4, 1952 2,680,899 Sebok et a1. June 15, 1954 FOREIGNPATENTS 111,737 Australia Oct. 24, 1940

